Bas C. Van Fraassen

Personal probability is now a familiar subject in epistemology, together with such more venerable notions as knowledge and belief. But there are severe strains between probability and belief; if either is taken as the more basic, the other may suffer. After explaining the difficulties of attempts to accommodate both, I shall propose a unified account which takes conditional personal probability as basic. Full belief is therefore a defined, derivative notion. Yet we will still be able to picture opinion as follows: my subjective probability is only a grading of the possibilities left open by my beliefs. My conditional probabilities generally derive from the strongest belief I can maintain when admitting the relevant condition

Constructive empiricism is indeed set squarely within a common sense realism that was foreign to much of the empiricist tradition. But I do not see this common sense realism, which I take myself to share with many scientific realists, as harboring or leading to scientific realism. That is in part because of the way I separate the opposition between empiricist and realist understanding of science from other issues that divide us in epistemology. This discussion brought to light our quite different conceptions of what is at issue between empiricists and realists in this area. After a response to McMullin's critique, however, I will be especially concerned to respond to his challenging proposal for a shift in the debate over realism concerning the sciences.

Professor Massey's exposition and analysis [5] of Professor Grünbaum's writings on metric aspects of space seem to me both very helpful in understanding those writings and to contain a considerable original contribution to the subject. Nevertheless I would like to argue that there is an alternative to Massey's explication which seems to me more faithful to Grünbaum's remarks; it seems at least to have the virtue of not forcing Grünbaum to reject the usual mathematical definitions of the notions used

Michel Ghins and I are both empiricists, and agree significantly in our critique of “traditional” empiricist epistemology. We differ however in some respects in our interpretation of the scientific enterprise. Ghins argues for a moderate scientific realism which includes the view that acceptance of a scientific theory will bring with it belief in the existence of all those entities, among the entities the theory postulates, that satisfy certain criteria. For Ghins these criteria derive from the criteria for legitimate affirmation of existence for any entities, the directly observable ones not being privileged in that respect. They are roughly that the putatively existing entity should according to the accepted theory manifest itself in our experience, and display a certain permanence and invariance. My disagreement on this topic derives from a larger difference concerning the relation between experience, existence, and theory

Metaphysicians speak of laws of nature in terms of necessity and universality; scientists, in terms of symmetry and invariance. In this book van Fraassen argues that no metaphysical account of laws can succeed. He analyzes and rejects the arguments that there are laws of nature, or that we must believe there are, and argues that we should disregard the idea of law as an adequate clue to science. After exploring what this means for general epistemology, the author develops the empiricist view of science as a construction of models to represent the phenomena.

The opposition between empiricism and realism with respect to science is old: it appeared clearly in the seventeenth century sense of superiority of the ‘mechanical philosophy’ to Scholastic metaphysics, and continued for the next three centuries’ debates over the philosophical foundations of physics. Empiricist views developed by the logical positivists of Vienna and Berlin were defeated by the emergence of scientific realism in the mid‐twentieth century. This defeat was largely due to the inadequacy of the positivist theories of meaning and language. To present a viable empiricist account of science, we need conceptions of theory structure, truth, and empirical adequacy that are essentially independent of a theory's linguistic formulation. Correlative to this discussion of the relationship between theory and world is the question what it is to accept a scientific theory––how much belief is involved? And what is involved other than belief? The position to be developed here will view scientific activity as one of construction rather than discovery: construction of models that must be adequate to the observable phenomena, and not discovery of the truth about postulated unobservable parts of nature. Acceptance of a scientific theory so viewed will have an irreducible pragmatic dimension in addition to involving only a modest amount of belief.

The attempt to formulate a viable empiricist and non-foundationalist epistemology of science faces four problems here confronted. The first is an apparent loss of objectivity in science, in the conditions of use of models in applied science. The second derives from the theory-infection of scientific language, with an apparent loss of objective conditions of truth and reference. The third, often cited as objection to The Scientific Image, is the apparent theory-dependence of the distinction between what is and is not observable. The fourth and last is the loss of the possibility of objective evaluation of rationality in scientific methodology. It is argued that each of these problems is illusory